1. Field of the Invention
This invention pertains generally to optical switching systems, and more particularly to an optical wavelength channel cross-connect switch.
2. Description of Related Art
Wavelength-division multiplexing (WDM) is an important technology for providing high speed optical communications. Wavelength-division multiplexing (WDM) is an approach that exploits the huge bandwidth of optical transmission by multiplexing a number of discrete frequencies over the same optical link. The optical transmission spectrum under WDM is carved up into a number of discrete non-overlapping wavelength (or frequency) bands. Each wavelength supports a single communication channel, which may be further divided, such as by time multiplexing to support the transmission of a number of data streams on the channel.
The progress of optical WDM networks has been rapid and all-optical cross-connect switching systems have been implemented which allow any wavelength channel on a group of input fibers to be routed to any channel on a group of output fibers. For example, consider the case of eight optical fiber inputs and eight optical fiber outputs, with each fiber supporting one hundred wavelength channels. Using an optical wavelength-selective cross connect (WSXC) up to eight hundred channels are cross connected for output on the eight output fibers.
One form of all-optical wavelength-selective cross connect (WSXC) employs two-dimensional arrays of two-axis beam steering mirrors. These so-called 3D mirror arrays are typically fabricated utilizing micro-electromechanical systems (MEMS) techniques. The mirror arrays route a signal from a particular optical input to a desired optical output as selected on a two-dimensional grid. These cross-connect switches have a complicated structure requiring sophisticated control electronics, and they suffer from high power consumption.
Another approach to creating an all-optical cross-connect switch is based on demultiplexing the input, then using a cross-connect switch for each wavelength, after which the wavelengths are multiplexed back onto the output fibers. The approach is shown in FIG. 1, with wavelengths from a set of input fibers being separated into individual wavelength bands with a demultiplexer. A switching function is then performed on the individual wavelengths wherein an N×N switching matrix (8×8) is utilized to route signals to different multiplexers for combining the wavelengths into the set of output fibers. To support a configuration having eight input and output fibers, each supporting one hundred wavelengths, a total of 16 wavelength division multiplexers/demultiplexers are required, with 100 8×8 switches (one for each wavelength) along with 1600 fiber interconnections. It can be seen that wavelength selective cross-connects as currently embodied are complex and expensive to implement.
Therefore, a need exists for an all-optical cross-connect switch that allows cross connecting any of a plurality of wavelength channels from a group of optical fiber inputs to a group of optical fiber outputs. The present invention satisfies those needs, as well as others, and overcomes the deficiencies of previously developed wavelength selective optical cross-connect systems.